Economic and political pressures are now encouraging the development of pig and livestock farms, in lieu of tobacco farms for example. Recent developments however, have restricted the design of new or expanding pig farms. Concerns such as odor, air quality, and ground and surface water quality, often implicating the Clean Water Act and/or the Clean Air Act, drive the restrictions.
The number of animals housed in a barn, and the resultant manure, contribute to several odor and health related problems. Aside from the private and public nuisance concerns, acute odors also indicate the potential for disease and reduced hog propagation due to respiratory problems, for example. In humans, even lower concentrations (100-300 parts per billion) of gases such as hydrogen sulfide are known to cause eye irritation, headaches, diarrhea, nausea, and an inability to sleep. Many of the gases, bacteria, viruses, spores, and worms found in manure contribute to a number of illnesses that may inhibit the full maturation of the swine, result in condemnation of all or part of the pig, and/or result in their premature deaths. In addition, many pathogens harmful to animals may also be harmful to workers. The swine flu is illustrative. It is believed that insects and birds transfer these pathogens to the surrounding community.
In general, hog manure and urine contains or evolves into ammonia, hydrogen sulfide, methane, nitrates, trihalomethanes, spores of molds, and other contaminants. Research has shown that animal effluvia and the putrefactive gases resulting from animal and vegetable tissue are generally present in and around hog barns. Putrefaction produces highly odorous gases and compounds such as ammonia, amino acids, aromatic fatty acids, metabolites, mercaptans, indole, skatole, cresol, and alkaloid-like ptomaines such as tetramethylene-diamine and pentamethylene-diamine. Of course, the microbiological agents producing these gases are also present in and around barns.
In fact, one of the major concerns within the barn is the amount of dust caused by trampling of the feed and manure, and also from the dander of the animals. As the manure is trampled, it exudes through slots or grates in the concrete floor to a manure pit housed below the animal containment area. As the animals work the manure, odor-causing gases are also liberated. The dust is problematic in several ways. To begin with, particulate sizes of 0.7 to 1.5 microns readily settle within the alveoli of the lungs thereby causing respiratory ailments in pigs or other livestock. Airborne pathogens carried by the dust are thus transferred to the lungs of the livestock, thereby requiring antibiotic treatment. In fact, about 65% of animal diseases are caused due to dust. The same mechanism causes chronic obstructive pulmonary emphysema in humans, also known as "Farmer's Lung" or "Smoker's Lung".
Several methods have been developed to deal with these concerns. Filtration towers containing water and/or air-bio filters such as microfiltration sponges filter the barn air as it passes through. These systems are costly and labor intensive.
Another approach involves spraying oil on the floors and sides of the barn. As the oil accumulates, however, it becomes increasingly more difficult to move across the slippery surfaces of the barn. Furthermore, the oil may contribute to a structural breakdown of the barn.
Ventilation is another approach. In tunnel ventilation, the air within a building is completely replaced about every 30 seconds. In winter, however, this method is often cost prohibitive due to heat loss. In recirculation ventilation, half of the air is vented outside of the building and the other half is routed back into the barn. Again, this method also causes heat loss, but to a lesser extent. Additionally, the dust and odors are not completely removed. In general, the dust vented to the outside air has been found to travel anywhere from five to eight miles from the source, thereby causing epidemics and disease transfer from farm to farm or from farm to community. Recently, 200,000 animals were destroyed in a single province of Spain due to disease transferred by this mechanism. Taiwan destroyed their entire swine herd after an outbreak of hoof and mouth disease.
Finally, another approach to alleviating the dust is the spraying of probiotic nonpathogenic bacteria. The probiotic bacteria denitrify ammonia-causing gases and also bind to hydrogen sulfide thereby inhibiting odor. The method can be very costly because the temperature must be maintained at a constant temperature of 65-100 degrees Fahrenheit. Although characterized as nonpathogenic, if the probiotic bacteria are cross-contaminated by pseudomonas or E-coli for example, rampant disease can result. The method is also labor intensive given that the bacteria must be applied every day.
In addition to dust and odor, high humidity is also a concern in the barn. During the fall, winter, and spring, relative humidity levels of approximately 90% are not uncommon.
Recent attention has also focused on the need for environmental control in and around manure pits. Odors resulting from many manure pits and containment areas significantly detract from the use, enjoyment, and value of surrounding property. The formation of a manure crust in certain pits seals the containment area thereby preventing natural aeration and contributing to an unbalanced anaerobic state. This results in an acute and malodorous buildup of methane, hydrogen sulfide, and other gases. The formation of the crust also creates a breeding ground for flies, believed to be another primary disease vector from the farm to the surrounding community. Birds, in turn, often feed on the fly larvae and constitute a secondary disease vector. Finally, crust formation also inhibits slurry removal thereby contributing to an inoperable pit. The benefits of odor control and crust prevention thus become obvious.
A recent study by the U.S. Senate details the magnitude of environmental problems caused by animal waste. The findings indicate that the amount of animal manure produced annually is conservatively estimated to be 130 times greater than the amount of human waste produced. Stated another way, a 50,000-acre farm in Utah has been cited as potentially producing more waste than the entire city of Los Angeles. Other findings indicate that agricultural officials consider 60% of rivers and streams "impaired", with agricultural runoff the largest contributor to the pollution. Anecdotally, a 30,000 fish kill resulted from a weekend hog manure spill in Iowa. As such, efforts are underway to impose national standards on livestock producers. An improvement in the treatment of the manure is therefore needed.
On a state level, certain areas such as North Carolina have enacted moratoriums on new or expanding hog farms. North Carolina has also granted counties zoning control over farms with more than 5,000 hogs. Industry experts warn that as more restrictions are placed on U.S. hog farms, pork production could move to other countries thereby damaging family farms and sending food profits overseas. The net result of further restrictions limits the land use and therefore detracts from the profitability of the farmland.
Several methods of storage and/or disposal include aboveground slurry storage, belowground slurry storage, anaerobic pits with or without cover, aerated pits, oxidation ditches, and solid/liquid separation. Each method has its advantages and disadvantages such as costliness and ineffective odor control. To mitigate the odors, pit additives are often used with little to moderate success.
Scientists have attempted to reduce odors from the annual spring runoff into the North Saskatchewan River at Edmonton, Alberta. The odors have been characterized as septic, manure, musty, earthy, and hay-like. Despite oxidative treatment, the odors persisted thereby supporting the scientists' belief of the futility of relying strictly on oxidative treatment. Other odor control methods have incorporated aeration with costly additives to control the odors.
Other efforts are underway to reduce or eliminate manure odors. For example, the University of Minnesota Agricultural Engineering department recently began a project to measure, chart, and record odors emitted from different livestock production sites around Minnesota. As one engineer states, there is currently very limited knowledge about the odor from hog production systems. The main thrust of the project is to develop a database to assist communities and pork producers in developing reasonable expectations about odor. At the national Center for Agricultural Utilization Research in Peoria, Ill., researchers sought one million dollars to attack the malodorous nature of manure. Other problems tabled for action include air and groundwater quality.
The use of ozone is well known as a disinfectant or sterilizing agent. In general, due to its disinfecting properties, ozone has not been considered as a viable or feasible alternative when treating manure pits or lagoons. The conventional wisdom is that disinfection caused by the use of ozone would interfere with the microbiological balance within wastewater slurries, wherein solids are digested through the use of activated sludge.
Furthermore, the use of ozone within a confined area is subject to OSHA regulations. Exposure to concentrations of one part per million for over 10 minutes often leads to irritation of the eyes, nose, throat, and other adverse symptoms. The designs of ozone dispersal systems are often disadvantaged by an uneven distribution of ozone and therefore contribute to animal and human exposure to excess levels of ozone. A system designed to prevent accidental exposure to excessive levels of ozone would therefore be an improvement in the art.